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Effect of Age and Gender on Muscle Strength and Control in Young Athletes

More and more children are participating in sports programs. This means more children than ever before will have sports injuries. In fact studies show one-third of these children will have an injury that requires treatment. The ankle and knee seem to be the areas injured most often. Girls have four to eight times more knee ligament injuries compared to boys.

In this study researchers look at strength differences in male and female athletes ages nine to 17. The goal was to see if age and gender have an effect on muscle strength and control during jumping and landing.

A sports injury test made up of three specific tests was given to 1,140 young athletes. The three tests included 1) flexion (hamstring) and extension (quadriceps) strength of the leg, 2) drop-jump test, and 3) single leg hop test.

The drop-jump test was videotaped to show hip, knee, and ankle alignment. Each athlete jumped off a box and landed with both feet on the floor. The box was 30 cm (about eight inches) high. The hop test was made up of two types of hopping skills based on time and distance.

Results showed maximum strength for extension in girls at age 13 and both flexion and extension in boys at 14. Only slight increases in flexion strength were noted for girls ages nine to 11. This may suggest a need for hamstring strengthening in young female athletes. As boys got older (ages 14 to 17) their strength increased more than girls.

There was no difference in limb alignment between the boys and girls with the drop-jump test. The authors say this suggests some factor other than alignment for knee ligament injuries in girls. And for the third test, increased strength with older age didn't improve results of the hop test.

The authors say this is one of the largest studies ever done on strength differences by age and gender in young athletes. Information on the development of muscle strength and control of the lower leg during jumping and landing may help prevent future knee ligament injuries. They propose a longer study is needed before any final conclusions can be made.

References: Sue D. Barber-Westin, et al. Jump-Land Characteristics and Muscle Length Development in Young Athletes. A Gender Comparison of 1140 Athletes 9 to 17 Years of Age. In The American Journal of Sports Medicine. March 2006. Vol. 34. No. 3. Pp. 375-384.

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